1. Field of the Invention
This invention relates to a reflective display for displaying using outside light such as natural light and more particularly to an illumination structure of a reflective display used supplementally when there is only a little outside light.
2. Description of the Related Art
Display apparatuses which use a liquid crystal as an electro-optical substance are advantageous in that the structure is made in the form of a flat panel that is thin and light weight, and its power consumption is low. Therefore, such display apparatuses have been developed as displays of mobile apparatuses. An electro-optical substance such as a liquid crystal does not emit the light, but displays an image by allowing the outside light to be transmitted or shut off selectively. Such passive display apparatus is categorized into a transmission type and a reflection type depending on illumination type.
In a transmission display apparatus, a panel which holds, for example, a liquid crystal as an electro-optical substance between a pair of transparent substrates is fabricated. A light source (i.e., a "back light") for illumination is provided on the back side of the panel. An image is observed from the front of the panel. In the case of a transmission type, a back light is indispensable and, for example, a cold cathode tube is used as the light source. As the result, a back light consumes the major part of power among components in a whole display. Therefore the transmission type is not suitable as a display of a mobile apparatus. On the other hand, in a reflective display, a reflection plate is provided on the back side of a panel, and an outside light such as natural light is incident from the front. An image is observed from the front utilizing the reflected light. Differently from the transmission type, a light source for back lighting is not used in the reflection type; therefore the power consumption is relatively low in the reflection type, and is thus suitable as a display of a mobile apparatus. However, because an image can not be viewed in an environment of scarce outside light such as at night time in the case of a reflective display, this is a problem to be solved.